Finding dads relos

Hi This is a very long shot but i'm trying to find dads relo's in England. My dad's name was Geoffrey Shackleton form Glenmore Park in NSW, Australia. Dad past away 2 years ago. I would like to get in contact with dads Relos but all we know is that he regualrly wrote to them but none of dads children have found there name or address..if you can help that would be great..